use crate::vector::Vec3;

pub trait Camera
{
    /// Returns the camera position.
    fn position(&self) -> Vec3<f32>;

    /// Returns the position of the camera target.
    fn target(&self) -> Vec3<f32>;

    /// Returns the direction the camera is looking.
    fn direction(&self) -> Vec3<f32>
    {
        self.target() - self.position()
    }

    /// Returns the right direction relative from where the camera is looking.
    fn right(&self) -> Vec3<f32>
    {
        self.direction().cross(&self.global_up()).normalize()
    }

    /// Returns the left direction relative from where the camera is looking.
    fn left(&self) -> Vec3<f32>
    {
        -self.right()
    }

    /// Returns the upwards direction relative from where the camera is looking.
    fn up(&self) -> Vec3<f32>
    {
        let rev_direction = -self.direction();

        rev_direction.cross(&self.right())
    }

    /// Returns the downwards direction relative from where the camera is looking.
    fn down(&self) -> Vec3<f32>
    {
        -self.up()
    }

    /// Returns the global direction upwards.
    ///
    /// The default implementation which returns [`Vec3::UP`] should be fine in most
    /// cases.
    fn global_up(&self) -> Vec3<f32>
    {
        Vec3::UP
    }
}